In the processing of substrates such as semiconductors and displays, layers are formed on the substrate, and then etched to form features such as electrically conducting interconnects, contacts, vias, gates and barriers. For example, a pattern of electrical interconnect lines can be made by depositing a metal-containing conductor on the substrate, forming a patterned etch resistant material on the conductor, etching the conductor to form the interconnect lines, removing remnant resist, and depositing dielectric over the etched features. The dielectric layer can be further etched to form contact holes or vias that expose the underlying metal-containing conductor material or other substrate layers. Electrically conducting material is then deposited into the etched holes or trenches to electrically contact the underlying conductor. For example, in the formation of copper-containing interconnects, the dielectric layer can be etched to form contact holes that expose an underlying copper conductor material. A thin seed layer of copper can be deposited over the exposed conductor and contact hole to facilitate subsequent copper electroplating processes to fill the contact holes.
However, contaminants and undesirable surface material on the metal-containing conductor require cleaning of the exposed conductor surfaces before subsequent process steps are performed. For example, a native oxide film often forms on a conductor exposed to oxygen species during an intermediate process step, for example, during a resist stripping process in which an oxygen-containing gas plasma is used to strip resist, or when transferring the substrate between different chambers. The oxide films increase the electrical resistance at the contact interface between conductor surfaces. The surface material can also have residual process deposits from previous processes, such as for example carbon-containing, silicon-containing, fluorine-containing, and nitrogen-containing process residues. These process deposits can cause voids or other irregularities to form at the interface between the exposed and deposited materials.
Substrate cleaning chambers, also known as pre-clean chambers, are used to clean oxide films and other undesirable process deposits from the substrate surface prior to processing and in between processing steps. During the cleaning process, the substrate is supported in the cleaning chamber and an energized cleaning gas is formed in a remote gas chamber and introduced into the chamber. The cleaning gas reacts with and removes the surface residues. In some processes, the substrate heating pedestal includes a heating element to control the temperature of the substrate during cleaning.
However, one problem with the use of an energized cleaning gas in such cleaning processes is that it is difficult to control the energy of the radical and ionic species of the excited cleaning gas. Higher energy collisions between the cleaning gas and the substrate surface can cause damage to the underlying substrate. Lighter ions in the cleaning gas, such as for example H+ can also be detrimental when they penetrate the surface of the substrate to damage underlying dielectric layers. Thus, it is desirable to control the energy of, and type of energized species introduced into the process chamber.
Another problem is that the cleaning gas often etches away and erodes the remote chamber wall surrounding the excitation region of the remote within a gas energizer, and can even etch and erode components inside the cleaning chamber. Such erosion damages these components, and if the component is an integral part of the chamber, the chamber must be shut down to allow the component to be refurbished or replaced after a predetermined number of process cycles, which is undesirable. Conventional stainless steel walls and liners are particularly susceptible to erosion and require frequent replacement or refurbishment.
Yet another problem occurs when the substrate heating pedestal in the cleaning chamber that contacts the substrate, transfers contaminants and process residues deposits to the backside of the substrate or even scratches the substrate during the substrate transferring process. Substrate heating pedestals containing heating elements can also provide non-uniform heating across the surface of the substrate. Substrate heating pedestals having a substrate receiving surface made up of raised mesas and grooves allow flow of a heat transfer gas behind the substrate to improve temperature uniformity but still transfer undesirable amounts of process residues and deposits to the substrate.
Thus, it is desirable to have a cleaning chamber and gas energizer that can selectively filter energized gas species, for example, to filter out certain ionic species from the cleaning gas. It is also desirable to have chamber components that can be easily replaced or refurbished. It is further desirable to have a substrate heating pedestal that minimizes contamination of the substrate by the transfer of process deposits to the backside surface of the substrate. It is also desirable to have a substrate heating pedestal that allows a more uniform heating of the substrate.